1. Field of the Invention
The present invention relates to a communication device and a communication method, and specifically relates to a communication device and a communication method, whereby retention property can be maintained, and also writing processing time used for writing can be shortened, regarding nonvolatile memory which a wireless tag houses, for example, such as an IC card or IC chip or the like which performs proximity communication with a reader/writer.
2. Description of the Related Art
In recent years, proximity communication for performing wireless communication by noncontact at short range using IC (Integrated Circuit) cards and the like, has been used for, for example, electronic commuter passes, electronic money, and so forth, and also cellular phones having electronic commuter pass functions, and electronic money functions that take advantage of proximity communication, have come into widespread use.
Proximity communication has been standardized as, for example, ISO/IEC 14443, ISO/IEC 18092 (hereafter, also referred to as NFC (Near Field Communication)), and so forth. Here, of communication devices for performing proximity communication such as communication conforming to the NFC standard, or the like, communication devices such as IC cards, IC chips, and so forth for performing proximity communication with a reader/writer which outputs RF (Radio Frequency) signals, in response to signals from the reader/writer, are also referred to as wireless tags.
Wireless tags provide various types of services by housing nonvolatile memory such as EEPROM (Electrically Erasable Programmable Read Only Memory) or the like, and performing reading/writing of data to be exchanged with a reader/writer as to the nonvolatile memory by proximity communication, for example.
Note that, of wireless tags, there are batteryless wireless tags which operate with RF signals output by a reader/writer as the power source thereof. Batteryless wireless tags operate with RF signals output by a reader/writer as the power source thereof, and accordingly fail to obtain sufficient power at the time of being separated from a reader/writer. Therefore, for example, with a wireless tag, upon the wireless tag being separated from a reader/writer while access to built-in nonvolatile memory is performed, the wireless tag fails to operate, and memory corruption may occur, i.e., inconsistency may occur in data stored in the nonvolatile memory.
Also, with a wireless tag having battery (e.g., an IC chip housed in a cellular phone) as well, memory corruption may occur in the event that data to be written in nonvolatile memory is prevented from being received from a reader/writer by the wireless tag being separated from the reader/writer. As for a way to deal with memory corruption, there is a process wherein, with the nonvolatile memory of a wireless tag, the latest data is not overwritten on most recently written data, but is written on a recording region separated from the storage region of the most recently written data (e.g., see Japanese Patent Document No. 3702923).